var QR = (function() {
  // alignment pattern
  var adelta = [
    0, 11, 15, 19, 23, 27, 31, // force 1 pat
    16, 18, 20, 22, 24, 26, 28, 20, 22, 24, 24, 26, 28, 28, 22, 24, 24,
    26, 26, 28, 28, 24, 24, 26, 26, 26, 28, 28, 24, 26, 26, 26, 28, 28
  ]

  // version block
  var vpat = [
    0xc94, 0x5bc, 0xa99, 0x4d3, 0xbf6, 0x762, 0x847, 0x60d,
    0x928, 0xb78, 0x45d, 0xa17, 0x532, 0x9a6, 0x683, 0x8c9,
    0x7ec, 0xec4, 0x1e1, 0xfab, 0x08e, 0xc1a, 0x33f, 0xd75,
    0x250, 0x9d5, 0x6f0, 0x8ba, 0x79f, 0xb0b, 0x42e, 0xa64,
    0x541, 0xc69
  ]

  // final format bits with mask: level << 3 | mask
  var fmtword = [
    0x77c4, 0x72f3, 0x7daa, 0x789d, 0x662f, 0x6318, 0x6c41, 0x6976, // L
    0x5412, 0x5125, 0x5e7c, 0x5b4b, 0x45f9, 0x40ce, 0x4f97, 0x4aa0, // M
    0x355f, 0x3068, 0x3f31, 0x3a06, 0x24b4, 0x2183, 0x2eda, 0x2bed, // Q
    0x1689, 0x13be, 0x1ce7, 0x19d0, 0x0762, 0x0255, 0x0d0c, 0x083b // H
  ]

  // 4 per version: number of blocks 1,2; data width; ecc width
  var eccblocks = [
    1, 0, 19, 7, 1, 0, 16, 10, 1, 0, 13, 13, 1, 0, 9, 17,
    1, 0, 34, 10, 1, 0, 28, 16, 1, 0, 22, 22, 1, 0, 16, 28,
    1, 0, 55, 15, 1, 0, 44, 26, 2, 0, 17, 18, 2, 0, 13, 22,
    1, 0, 80, 20, 2, 0, 32, 18, 2, 0, 24, 26, 4, 0, 9, 16,
    1, 0, 108, 26, 2, 0, 43, 24, 2, 2, 15, 18, 2, 2, 11, 22,
    2, 0, 68, 18, 4, 0, 27, 16, 4, 0, 19, 24, 4, 0, 15, 28,
    2, 0, 78, 20, 4, 0, 31, 18, 2, 4, 14, 18, 4, 1, 13, 26,
    2, 0, 97, 24, 2, 2, 38, 22, 4, 2, 18, 22, 4, 2, 14, 26,
    2, 0, 116, 30, 3, 2, 36, 22, 4, 4, 16, 20, 4, 4, 12, 24,
    2, 2, 68, 18, 4, 1, 43, 26, 6, 2, 19, 24, 6, 2, 15, 28,
    4, 0, 81, 20, 1, 4, 50, 30, 4, 4, 22, 28, 3, 8, 12, 24,
    2, 2, 92, 24, 6, 2, 36, 22, 4, 6, 20, 26, 7, 4, 14, 28,
    4, 0, 107, 26, 8, 1, 37, 22, 8, 4, 20, 24, 12, 4, 11, 22,
    3, 1, 115, 30, 4, 5, 40, 24, 11, 5, 16, 20, 11, 5, 12, 24,
    5, 1, 87, 22, 5, 5, 41, 24, 5, 7, 24, 30, 11, 7, 12, 24,
    5, 1, 98, 24, 7, 3, 45, 28, 15, 2, 19, 24, 3, 13, 15, 30,
    1, 5, 107, 28, 10, 1, 46, 28, 1, 15, 22, 28, 2, 17, 14, 28,
    5, 1, 120, 30, 9, 4, 43, 26, 17, 1, 22, 28, 2, 19, 14, 28,
    3, 4, 113, 28, 3, 11, 44, 26, 17, 4, 21, 26, 9, 16, 13, 26,
    3, 5, 107, 28, 3, 13, 41, 26, 15, 5, 24, 30, 15, 10, 15, 28,
    4, 4, 116, 28, 17, 0, 42, 26, 17, 6, 22, 28, 19, 6, 16, 30,
    2, 7, 111, 28, 17, 0, 46, 28, 7, 16, 24, 30, 34, 0, 13, 24,
    4, 5, 121, 30, 4, 14, 47, 28, 11, 14, 24, 30, 16, 14, 15, 30,
    6, 4, 117, 30, 6, 14, 45, 28, 11, 16, 24, 30, 30, 2, 16, 30,
    8, 4, 106, 26, 8, 13, 47, 28, 7, 22, 24, 30, 22, 13, 15, 30,
    10, 2, 114, 28, 19, 4, 46, 28, 28, 6, 22, 28, 33, 4, 16, 30,
    8, 4, 122, 30, 22, 3, 45, 28, 8, 26, 23, 30, 12, 28, 15, 30,
    3, 10, 117, 30, 3, 23, 45, 28, 4, 31, 24, 30, 11, 31, 15, 30,
    7, 7, 116, 30, 21, 7, 45, 28, 1, 37, 23, 30, 19, 26, 15, 30,
    5, 10, 115, 30, 19, 10, 47, 28, 15, 25, 24, 30, 23, 25, 15, 30,
    13, 3, 115, 30, 2, 29, 46, 28, 42, 1, 24, 30, 23, 28, 15, 30,
    17, 0, 115, 30, 10, 23, 46, 28, 10, 35, 24, 30, 19, 35, 15, 30,
    17, 1, 115, 30, 14, 21, 46, 28, 29, 19, 24, 30, 11, 46, 15, 30,
    13, 6, 115, 30, 14, 23, 46, 28, 44, 7, 24, 30, 59, 1, 16, 30,
    12, 7, 121, 30, 12, 26, 47, 28, 39, 14, 24, 30, 22, 41, 15, 30,
    6, 14, 121, 30, 6, 34, 47, 28, 46, 10, 24, 30, 2, 64, 15, 30,
    17, 4, 122, 30, 29, 14, 46, 28, 49, 10, 24, 30, 24, 46, 15, 30,
    4, 18, 122, 30, 13, 32, 46, 28, 48, 14, 24, 30, 42, 32, 15, 30,
    20, 4, 117, 30, 40, 7, 47, 28, 43, 22, 24, 30, 10, 67, 15, 30,
    19, 6, 118, 30, 18, 31, 47, 28, 34, 34, 24, 30, 20, 61, 15, 30
  ]

  // Galois field log table
  var glog = [
    0xff, 0x00, 0x01, 0x19, 0x02, 0x32, 0x1a, 0xc6, 0x03, 0xdf, 0x33, 0xee, 0x1b, 0x68, 0xc7, 0x4b,
    0x04, 0x64, 0xe0, 0x0e, 0x34, 0x8d, 0xef, 0x81, 0x1c, 0xc1, 0x69, 0xf8, 0xc8, 0x08, 0x4c, 0x71,
    0x05, 0x8a, 0x65, 0x2f, 0xe1, 0x24, 0x0f, 0x21, 0x35, 0x93, 0x8e, 0xda, 0xf0, 0x12, 0x82, 0x45,
    0x1d, 0xb5, 0xc2, 0x7d, 0x6a, 0x27, 0xf9, 0xb9, 0xc9, 0x9a, 0x09, 0x78, 0x4d, 0xe4, 0x72, 0xa6,
    0x06, 0xbf, 0x8b, 0x62, 0x66, 0xdd, 0x30, 0xfd, 0xe2, 0x98, 0x25, 0xb3, 0x10, 0x91, 0x22, 0x88,
    0x36, 0xd0, 0x94, 0xce, 0x8f, 0x96, 0xdb, 0xbd, 0xf1, 0xd2, 0x13, 0x5c, 0x83, 0x38, 0x46, 0x40,
    0x1e, 0x42, 0xb6, 0xa3, 0xc3, 0x48, 0x7e, 0x6e, 0x6b, 0x3a, 0x28, 0x54, 0xfa, 0x85, 0xba, 0x3d,
    0xca, 0x5e, 0x9b, 0x9f, 0x0a, 0x15, 0x79, 0x2b, 0x4e, 0xd4, 0xe5, 0xac, 0x73, 0xf3, 0xa7, 0x57,
    0x07, 0x70, 0xc0, 0xf7, 0x8c, 0x80, 0x63, 0x0d, 0x67, 0x4a, 0xde, 0xed, 0x31, 0xc5, 0xfe, 0x18,
    0xe3, 0xa5, 0x99, 0x77, 0x26, 0xb8, 0xb4, 0x7c, 0x11, 0x44, 0x92, 0xd9, 0x23, 0x20, 0x89, 0x2e,
    0x37, 0x3f, 0xd1, 0x5b, 0x95, 0xbc, 0xcf, 0xcd, 0x90, 0x87, 0x97, 0xb2, 0xdc, 0xfc, 0xbe, 0x61,
    0xf2, 0x56, 0xd3, 0xab, 0x14, 0x2a, 0x5d, 0x9e, 0x84, 0x3c, 0x39, 0x53, 0x47, 0x6d, 0x41, 0xa2,
    0x1f, 0x2d, 0x43, 0xd8, 0xb7, 0x7b, 0xa4, 0x76, 0xc4, 0x17, 0x49, 0xec, 0x7f, 0x0c, 0x6f, 0xf6,
    0x6c, 0xa1, 0x3b, 0x52, 0x29, 0x9d, 0x55, 0xaa, 0xfb, 0x60, 0x86, 0xb1, 0xbb, 0xcc, 0x3e, 0x5a,
    0xcb, 0x59, 0x5f, 0xb0, 0x9c, 0xa9, 0xa0, 0x51, 0x0b, 0xf5, 0x16, 0xeb, 0x7a, 0x75, 0x2c, 0xd7,
    0x4f, 0xae, 0xd5, 0xe9, 0xe6, 0xe7, 0xad, 0xe8, 0x74, 0xd6, 0xf4, 0xea, 0xa8, 0x50, 0x58, 0xaf
  ]

  // Galios field exponent table
  var gexp = [
    0x01, 0x02, 0x04, 0x08, 0x10, 0x20, 0x40, 0x80, 0x1d, 0x3a, 0x74, 0xe8, 0xcd, 0x87, 0x13, 0x26,
    0x4c, 0x98, 0x2d, 0x5a, 0xb4, 0x75, 0xea, 0xc9, 0x8f, 0x03, 0x06, 0x0c, 0x18, 0x30, 0x60, 0xc0,
    0x9d, 0x27, 0x4e, 0x9c, 0x25, 0x4a, 0x94, 0x35, 0x6a, 0xd4, 0xb5, 0x77, 0xee, 0xc1, 0x9f, 0x23,
    0x46, 0x8c, 0x05, 0x0a, 0x14, 0x28, 0x50, 0xa0, 0x5d, 0xba, 0x69, 0xd2, 0xb9, 0x6f, 0xde, 0xa1,
    0x5f, 0xbe, 0x61, 0xc2, 0x99, 0x2f, 0x5e, 0xbc, 0x65, 0xca, 0x89, 0x0f, 0x1e, 0x3c, 0x78, 0xf0,
    0xfd, 0xe7, 0xd3, 0xbb, 0x6b, 0xd6, 0xb1, 0x7f, 0xfe, 0xe1, 0xdf, 0xa3, 0x5b, 0xb6, 0x71, 0xe2,
    0xd9, 0xaf, 0x43, 0x86, 0x11, 0x22, 0x44, 0x88, 0x0d, 0x1a, 0x34, 0x68, 0xd0, 0xbd, 0x67, 0xce,
    0x81, 0x1f, 0x3e, 0x7c, 0xf8, 0xed, 0xc7, 0x93, 0x3b, 0x76, 0xec, 0xc5, 0x97, 0x33, 0x66, 0xcc,
    0x85, 0x17, 0x2e, 0x5c, 0xb8, 0x6d, 0xda, 0xa9, 0x4f, 0x9e, 0x21, 0x42, 0x84, 0x15, 0x2a, 0x54,
    0xa8, 0x4d, 0x9a, 0x29, 0x52, 0xa4, 0x55, 0xaa, 0x49, 0x92, 0x39, 0x72, 0xe4, 0xd5, 0xb7, 0x73,
    0xe6, 0xd1, 0xbf, 0x63, 0xc6, 0x91, 0x3f, 0x7e, 0xfc, 0xe5, 0xd7, 0xb3, 0x7b, 0xf6, 0xf1, 0xff,
    0xe3, 0xdb, 0xab, 0x4b, 0x96, 0x31, 0x62, 0xc4, 0x95, 0x37, 0x6e, 0xdc, 0xa5, 0x57, 0xae, 0x41,
    0x82, 0x19, 0x32, 0x64, 0xc8, 0x8d, 0x07, 0x0e, 0x1c, 0x38, 0x70, 0xe0, 0xdd, 0xa7, 0x53, 0xa6,
    0x51, 0xa2, 0x59, 0xb2, 0x79, 0xf2, 0xf9, 0xef, 0xc3, 0x9b, 0x2b, 0x56, 0xac, 0x45, 0x8a, 0x09,
    0x12, 0x24, 0x48, 0x90, 0x3d, 0x7a, 0xf4, 0xf5, 0xf7, 0xf3, 0xfb, 0xeb, 0xcb, 0x8b, 0x0b, 0x16,
    0x2c, 0x58, 0xb0, 0x7d, 0xfa, 0xe9, 0xcf, 0x83, 0x1b, 0x36, 0x6c, 0xd8, 0xad, 0x47, 0x8e, 0x00
  ]

  // Working buffers:
  // data input and ecc append, image working buffer, fixed part of image, run lengths for badness
  var strinbuf = []
  var eccbuf = []
  var qrframe = []
  var framask = []
  var rlens = []
  // Control values - width is based on version, last 4 are from table.
  var version, width, neccblk1, neccblk2, datablkw, eccblkwid
  var ecclevel = 2
  // set bit to indicate cell in qrframe is immutable.  symmetric around diagonal
  function setmask(x, y) {
    var bt
    if (x > y) {
      bt = x
      x = y
      y = bt
    }
    // y*y = 1+3+5...
    bt = y
    bt *= y
    bt += y
    bt >>= 1
    bt += x
    framask[bt] = 1
  }

  // enter alignment pattern - black to qrframe, white to mask (later black frame merged to mask)
  function putalign(x, y) {
    var j

    qrframe[x + width * y] = 1
    for (j = -2; j < 2; j++) {
      qrframe[(x + j) + width * (y - 2)] = 1
      qrframe[(x - 2) + width * (y + j + 1)] = 1
      qrframe[(x + 2) + width * (y + j)] = 1
      qrframe[(x + j + 1) + width * (y + 2)] = 1
    }
    for (j = 0; j < 2; j++) {
      setmask(x - 1, y + j)
      setmask(x + 1, y - j)
      setmask(x - j, y - 1)
      setmask(x + j, y + 1)
    }
  }

  // ========================================================================
  // Reed Solomon error correction
  // exponentiation mod N
  function modnn(x) {
    while (x >= 255) {
      x -= 255
      x = (x >> 8) + (x & 255)
    }
    return x
  }

  var genpoly = []

  // Calculate and append ECC data to data block.  Block is in strinbuf, indexes to buffers given.
  function appendrs(data, dlen, ecbuf, eclen) {
    var i, j, fb

    for (i = 0; i < eclen; i++) { strinbuf[ecbuf + i] = 0 }
    for (i = 0; i < dlen; i++) {
      fb = glog[strinbuf[data + i] ^ strinbuf[ecbuf]]
      if (fb != 255) /* fb term is non-zero */ {
        for (j = 1; j < eclen; j++) { strinbuf[ecbuf + j - 1] = strinbuf[ecbuf + j] ^ gexp[modnn(fb + genpoly[eclen - j])] }
      } else {
        for (j = ecbuf; j < ecbuf + eclen; j++) { strinbuf[j] = strinbuf[j + 1] }
      }
      strinbuf[ecbuf + eclen - 1] = fb == 255 ? 0 : gexp[modnn(fb + genpoly[0])]
    }
  }
  // ========================================================================
  // Frame data insert following the path rules

  // check mask - since symmetrical use half.
  function ismasked(x, y) {
    var bt
    if (x > y) {
      bt = x
      x = y
      y = bt
    }
    bt = y
    bt += y * y
    bt >>= 1
    bt += x
    return framask[bt]
  }

  // ========================================================================
  //  Apply the selected mask out of the 8.
  function applymask(m) {
    var x, y, r3x, r3y

    switch (m) {
      case 0:
        for (y = 0; y < width; y++) {
          for (x = 0; x < width; x++) {
            if (!((x + y) & 1) && !ismasked(x, y)) { qrframe[x + y * width] ^= 1 }
          }
        }
        break
      case 1:
        for (y = 0; y < width; y++) {
          for (x = 0; x < width; x++) {
            if (!(y & 1) && !ismasked(x, y)) { qrframe[x + y * width] ^= 1 }
          }
        }
        break
      case 2:
        for (y = 0; y < width; y++) {
          for (r3x = 0, x = 0; x < width; x++, r3x++) {
            if (r3x == 3) { r3x = 0 }
            if (!r3x && !ismasked(x, y)) { qrframe[x + y * width] ^= 1 }
          }
        }
        break
      case 3:
        for (r3y = 0, y = 0; y < width; y++, r3y++) {
          if (r3y == 3) { r3y = 0 }
          for (r3x = r3y, x = 0; x < width; x++, r3x++) {
            if (r3x == 3) { r3x = 0 }
            if (!r3x && !ismasked(x, y)) { qrframe[x + y * width] ^= 1 }
          }
        }
        break
      case 4:
        for (y = 0; y < width; y++) {
          for (r3x = 0, r3y = ((y >> 1) & 1), x = 0; x < width; x++, r3x++) {
            if (r3x == 3) {
              r3x = 0
              r3y = !r3y
            }
            if (!r3y && !ismasked(x, y)) { qrframe[x + y * width] ^= 1 }
          }
        }
        break
      case 5:
        for (r3y = 0, y = 0; y < width; y++, r3y++) {
          if (r3y == 3) { r3y = 0 }
          for (r3x = 0, x = 0; x < width; x++, r3x++) {
            if (r3x == 3) { r3x = 0 }
            if (!((x & y & 1) + !(!r3x | !r3y)) && !ismasked(x, y)) { qrframe[x + y * width] ^= 1 }
          }
        }
        break
      case 6:
        for (r3y = 0, y = 0; y < width; y++, r3y++) {
          if (r3y == 3) { r3y = 0 }
          for (r3x = 0, x = 0; x < width; x++, r3x++) {
            if (r3x == 3) { r3x = 0 }
            if (!(((x & y & 1) + (r3x && (r3x == r3y))) & 1) && !ismasked(x, y)) { qrframe[x + y * width] ^= 1 }
          }
        }
        break
      case 7:
        for (r3y = 0, y = 0; y < width; y++, r3y++) {
          if (r3y == 3) { r3y = 0 }
          for (r3x = 0, x = 0; x < width; x++, r3x++) {
            if (r3x == 3) { r3x = 0 }
            if (!(((r3x && (r3x == r3y)) + ((x + y) & 1)) & 1) && !ismasked(x, y)) { qrframe[x + y * width] ^= 1 }
          }
        }
        break
    }
    return
  }

  // Badness coefficients.
  var N1 = 3
  var N2 = 3
  var N3 = 40
  var N4 = 10

  // Using the table of the length of each run, calculate the amount of bad image
  // - long runs or those that look like finders; called twice, once each for X and Y
  function badruns(length) {
    var i
    var runsbad = 0
    for (i = 0; i <= length; i++) {
      if (rlens[i] >= 5) { runsbad += N1 + rlens[i] - 5 }
    }
    // BwBBBwB as in finder
    for (i = 3; i < length - 1; i += 2) {
      if (rlens[i - 2] == rlens[i + 2] &&
        rlens[i + 2] == rlens[i - 1] &&
        rlens[i - 1] == rlens[i + 1] &&
        rlens[i - 1] * 3 == rlens[i]
        // white around the black pattern? Not part of spec
        &&
        (rlens[i - 3] == 0 // beginning
          ||
          i + 3 > length // end
          ||
          rlens[i - 3] * 3 >= rlens[i] * 4 || rlens[i + 3] * 3 >= rlens[i] * 4)
      ) { runsbad += N3 }
    }
    return runsbad
  }

  // Calculate how bad the masked image is - blocks, imbalance, runs, or finders.
  function badcheck() {
    var x, y, h, b, b1
    var thisbad = 0
    var bw = 0

    // blocks of same color.
    for (y = 0; y < width - 1; y++) {
      for (x = 0; x < width - 1; x++) {
        if ((qrframe[x + width * y] && qrframe[(x + 1) + width * y] &&
          qrframe[x + width * (y + 1)] && qrframe[(x + 1) + width * (y + 1)]) // all black
          ||
          !(qrframe[x + width * y] || qrframe[(x + 1) + width * y] ||
            qrframe[x + width * (y + 1)] || qrframe[(x + 1) + width * (y + 1)])) // all white
        { thisbad += N2 }
      }
    }

    // X runs
    for (y = 0; y < width; y++) {
      rlens[0] = 0
      for (h = b = x = 0; x < width; x++) {
        if ((b1 = qrframe[x + width * y]) == b) { rlens[h]++ } else { rlens[++h] = 1 }
        b = b1
        bw += b ? 1 : -1
      }
      thisbad += badruns(h)
    }

    // black/white imbalance
    if (bw < 0) { bw = -bw }

    var big = bw
    var count = 0
    big += big << 2
    big <<= 1
    while (big > width * width) { big -= width * width, count++ }
    thisbad += count * N4

    // Y runs
    for (x = 0; x < width; x++) {
      rlens[0] = 0
      for (h = b = y = 0; y < width; y++) {
        if ((b1 = qrframe[x + width * y]) == b) { rlens[h]++ } else { rlens[++h] = 1 }
        b = b1
      }
      thisbad += badruns(h)
    }
    return thisbad
  }

  function genframe(instring) {
    var x, y, k, t, v, i, j, m

    // find the smallest version that fits the string
    t = instring.length
    version = 0
    do {
      version++
      k = (ecclevel - 1) * 4 + (version - 1) * 16
      neccblk1 = eccblocks[k++]
      neccblk2 = eccblocks[k++]
      datablkw = eccblocks[k++]
      eccblkwid = eccblocks[k]
      k = datablkw * (neccblk1 + neccblk2) + neccblk2 - 3 + (version <= 9)
      if (t <= k) { break }
    } while (version < 40)

    // FIXME - insure that it fits insted of being truncated
    width = 17 + 4 * version

    // allocate, clear and setup data structures
    v = datablkw + (datablkw + eccblkwid) * (neccblk1 + neccblk2) + neccblk2
    for (t = 0; t < v; t++) { eccbuf[t] = 0 }
    strinbuf = instring.slice(0)

    for (t = 0; t < width * width; t++) { qrframe[t] = 0 }

    for (t = 0; t < (width * (width + 1) + 1) / 2; t++) { framask[t] = 0 }

    // insert finders - black to frame, white to mask
    for (t = 0; t < 3; t++) {
      k = 0
      y = 0
      if (t == 1) { k = (width - 7) }
      if (t == 2) { y = (width - 7) }
      qrframe[(y + 3) + width * (k + 3)] = 1
      for (x = 0; x < 6; x++) {
        qrframe[(y + x) + width * k] = 1
        qrframe[y + width * (k + x + 1)] = 1
        qrframe[(y + 6) + width * (k + x)] = 1
        qrframe[(y + x + 1) + width * (k + 6)] = 1
      }
      for (x = 1; x < 5; x++) {
        setmask(y + x, k + 1)
        setmask(y + 1, k + x + 1)
        setmask(y + 5, k + x)
        setmask(y + x + 1, k + 5)
      }
      for (x = 2; x < 4; x++) {
        qrframe[(y + x) + width * (k + 2)] = 1
        qrframe[(y + 2) + width * (k + x + 1)] = 1
        qrframe[(y + 4) + width * (k + x)] = 1
        qrframe[(y + x + 1) + width * (k + 4)] = 1
      }
    }

    // alignment blocks
    if (version > 1) {
      t = adelta[version]
      y = width - 7
      for (; ;) {
        x = width - 7
        while (x > t - 3) {
          putalign(x, y)
          if (x < t) { break }
          x -= t
        }
        if (y <= t + 9) { break }
        y -= t
        putalign(6, y)
        putalign(y, 6)
      }
    }

    // single black
    qrframe[8 + width * (width - 8)] = 1

    // timing gap - mask only
    for (y = 0; y < 7; y++) {
      setmask(7, y)
      setmask(width - 8, y)
      setmask(7, y + width - 7)
    }
    for (x = 0; x < 8; x++) {
      setmask(x, 7)
      setmask(x + width - 8, 7)
      setmask(x, width - 8)
    }

    // reserve mask-format area
    for (x = 0; x < 9; x++) { setmask(x, 8) }
    for (x = 0; x < 8; x++) {
      setmask(x + width - 8, 8)
      setmask(8, x)
    }
    for (y = 0; y < 7; y++) { setmask(8, y + width - 7) }

    // timing row/col
    for (x = 0; x < width - 14; x++) {
      if (x & 1) {
        setmask(8 + x, 6)
        setmask(6, 8 + x)
      } else {
        qrframe[(8 + x) + width * 6] = 1
        qrframe[6 + width * (8 + x)] = 1
      }
    }

    // version block
    if (version > 6) {
      t = vpat[version - 7]
      k = 17
      for (x = 0; x < 6; x++) {
        for (y = 0; y < 3; y++, k--) {
          if (1 & (k > 11 ? version >> (k - 12) : t >> k)) {
            qrframe[(5 - x) + width * (2 - y + width - 11)] = 1
            qrframe[(2 - y + width - 11) + width * (5 - x)] = 1
          } else {
            setmask(5 - x, 2 - y + width - 11)
            setmask(2 - y + width - 11, 5 - x)
          }
        }
      }
    }

    // sync mask bits - only set above for white spaces, so add in black bits
    for (y = 0; y < width; y++) {
      for (x = 0; x <= y; x++) {
        if (qrframe[x + width * y]) { setmask(x, y) }
      }
    }

    // convert string to bitstream
    // 8 bit data to QR-coded 8 bit data (numeric or alphanum, or kanji not supported)
    v = strinbuf.length

    // string to array
    for (i = 0; i < v; i++) { eccbuf[i] = strinbuf.charCodeAt(i) }
    strinbuf = eccbuf.slice(0)

    // calculate max string length
    x = datablkw * (neccblk1 + neccblk2) + neccblk2
    if (v >= x - 2) {
      v = x - 2
      if (version > 9) { v-- }
    }

    // shift and repack to insert length prefix
    i = v
    if (version > 9) {
      strinbuf[i + 2] = 0
      strinbuf[i + 3] = 0
      while (i--) {
        t = strinbuf[i]
        strinbuf[i + 3] |= 255 & (t << 4)
        strinbuf[i + 2] = t >> 4
      }
      strinbuf[2] |= 255 & (v << 4)
      strinbuf[1] = v >> 4
      strinbuf[0] = 0x40 | (v >> 12)
    } else {
      strinbuf[i + 1] = 0
      strinbuf[i + 2] = 0
      while (i--) {
        t = strinbuf[i]
        strinbuf[i + 2] |= 255 & (t << 4)
        strinbuf[i + 1] = t >> 4
      }
      strinbuf[1] |= 255 & (v << 4)
      strinbuf[0] = 0x40 | (v >> 4)
    }
    // fill to end with pad pattern
    i = v + 3 - (version < 10)
    while (i < x) {
      strinbuf[i++] = 0xec
      // buffer has room    if (i == x)      break;
      strinbuf[i++] = 0x11
    }

    // calculate and append ECC

    // calculate generator polynomial
    genpoly[0] = 1
    for (i = 0; i < eccblkwid; i++) {
      genpoly[i + 1] = 1
      for (j = i; j > 0; j--) {
        genpoly[j] = genpoly[j]
          ? genpoly[j - 1] ^ gexp[modnn(glog[genpoly[j]] + i)] : genpoly[j - 1]
      }
      genpoly[0] = gexp[modnn(glog[genpoly[0]] + i)]
    }
    for (i = 0; i <= eccblkwid; i++) { genpoly[i] = glog[genpoly[i]] } // use logs for genpoly[] to save calc step

    // append ecc to data buffer
    k = x
    y = 0
    for (i = 0; i < neccblk1; i++) {
      appendrs(y, datablkw, k, eccblkwid)
      y += datablkw
      k += eccblkwid
    }
    for (i = 0; i < neccblk2; i++) {
      appendrs(y, datablkw + 1, k, eccblkwid)
      y += datablkw + 1
      k += eccblkwid
    }
    // interleave blocks
    y = 0
    for (i = 0; i < datablkw; i++) {
      for (j = 0; j < neccblk1; j++) { eccbuf[y++] = strinbuf[i + j * datablkw] }
      for (j = 0; j < neccblk2; j++) { eccbuf[y++] = strinbuf[(neccblk1 * datablkw) + i + (j * (datablkw + 1))] }
    }
    for (j = 0; j < neccblk2; j++) { eccbuf[y++] = strinbuf[(neccblk1 * datablkw) + i + (j * (datablkw + 1))] }
    for (i = 0; i < eccblkwid; i++) {
      for (j = 0; j < neccblk1 + neccblk2; j++) { eccbuf[y++] = strinbuf[x + i + j * eccblkwid] }
    }
    strinbuf = eccbuf

    // pack bits into frame avoiding masked area.
    x = y = width - 1
    k = v = 1 // up, minus
    /* inteleaved data and ecc codes */
    m = (datablkw + eccblkwid) * (neccblk1 + neccblk2) + neccblk2
    for (i = 0; i < m; i++) {
      t = strinbuf[i]
      for (j = 0; j < 8; j++, t <<= 1) {
        if (0x80 & t) { qrframe[x + width * y] = 1 }
        do { // find next fill position
          if (v) { x-- } else {
            x++
            if (k) {
              if (y != 0) { y-- } else {
                x -= 2
                k = !k
                if (x == 6) {
                  x--
                  y = 9
                }
              }
            } else {
              if (y != width - 1) { y++ } else {
                x -= 2
                k = !k
                if (x == 6) {
                  x--
                  y -= 8
                }
              }
            }
          }
          v = !v
        } while (ismasked(x, y))
      }
    }

    // save pre-mask copy of frame
    strinbuf = qrframe.slice(0)
    t = 0 // best
    y = 30000 // demerit
    // for instead of while since in original arduino code
    // if an early mask was "good enough" it wouldn't try for a better one
    // since they get more complex and take longer.
    for (k = 0; k < 8; k++) {
      applymask(k) // returns black-white imbalance
      x = badcheck()
      if (x < y) { // current mask better than previous best?
        y = x
        t = k
      }
      if (t == 7) { break } // don't increment i to a void redoing mask
      qrframe = strinbuf.slice(0) // reset for next pass
    }
    if (t != k) // redo best mask - none good enough, last wasn't t
    { applymask(t) }

    // add in final mask/ecclevel bytes
    y = fmtword[t + ((ecclevel - 1) << 3)]
    // low byte
    for (k = 0; k < 8; k++, y >>= 1) {
      if (y & 1) {
        qrframe[(width - 1 - k) + width * 8] = 1
        if (k < 6) { qrframe[8 + width * k] = 1 } else { qrframe[8 + width * (k + 1)] = 1 }
      }
    }
    // high byte
    for (k = 0; k < 7; k++, y >>= 1) {
      if (y & 1) {
        qrframe[8 + width * (width - 7 + k)] = 1
        if (k) { qrframe[(6 - k) + width * 8] = 1 } else { qrframe[7 + width * 8] = 1 }
      }
    }

    // return image
    return qrframe
  }

  var _canvas = null
  var _size = null

  var api = {

    get ecclevel() {
      return ecclevel
    },

    set ecclevel(val) {
      ecclevel = val
    },

    get size() {
      return _size
    },

    set size(val) {
      _size = val
    },

    get canvas() {
      return _canvas
    },

    set canvas(el) {
      _canvas = el
    },

    getFrame: function(string) {
      return genframe(string)
    },

    draw: function(string, canvas, size, ecc) {
      ecclevel = ecc || ecclevel
      canvas = canvas || _canvas

      if (!canvas) {
        console.warn('No canvas provided to draw QR code in!')
        return
      }

      size = size || _size || Math.min(canvas.width, canvas.height)

      var frame = genframe(string)
      var ctx = canvas.ctx
      var px = Math.round(size / (width + 8))

      var roundedSize = px * (width + 8)
      var offset = Math.floor((size - roundedSize) / 2)

      size = roundedSize

      ctx.clearRect(0, 0, canvas.width, canvas.height)
      ctx.setFillStyle('#000000')

      for (var i = 0; i < width; i++) {
        for (var j = 0; j < width; j++) {
          if (frame[j * width + i]) {
            ctx.fillRect(px * (4 + i) + offset, px * (4 + j) + offset, px, px)
          }
        }
      }
      ctx.draw()
    }
  }

  module.exports = {
    api: api
  }
})()
